Influence of the volume share of fibers and the energy capacity of the matrix on the failure mechanism and strength stability of boroaluminum

Conclusions

• 1. In longitudinal tension of a boroaluminum type fiber composite material an increase in its volume share of fibers leads, in some cases, to a change in the failure mechanism from mixed to noncumulative. An increase in the energy content of the matrix has the same influence.

• 2. With an increase in energy content of the matrix there is an increase in the highest value of the minimum strength of boroaluminum reached, however, with higher volume shares of fibers.

• 3. For a boroaluminum-type fiber composite material there exists some optimum volume share of fibers at which the spread in values of its strength in the longitudinal direction is a minimum. With the optimum volume share of fibers the highest value of minimum strength is attained.

• 4. To attain the highest value of minimum strength of boroaluminum produced by a method in which the density of the areas of a strong bond between the matrix and fibers having an average strength of 2800 MPa (to a base of 25 mm) and a coefficient of variation of strength of 17% varies in different areas or in different lots of the fiber composite material from 0.1 to 1.0 it is necessary that the volume share of fibers V_f=0.2, 0.4, and 0.5 with the use of a matrix with a specific work for failure of 5 mJ/mm³, 19, 31, and 43 mJ/mm³, and 51 and 79 mJ/mm³, respectively. The guaranteed minimum in longitudinal strength of such fiber composite materials is 600, 850, 1100, 1200, 1250, and 1350 MPa, respectively.